Currently, there are two kinds of drum type beamless pumping units with good features: a chain pumping unit whose maximum stroke length may reach eight meters and which has a reasonable running curve and a desirable energy saving efficiency. However, this chain pumping unit is short in the bellows; the chains are distributed vertically and are too long to be lubricated. The abrasion of the chains results in a reversing stroke. The chains are difficult to repair and the maintenance cost is prohibitively high. In addition, the stroke length of the chain pumping unit cannot be adjusted. The other one is a drum type electric-reversing pumping unit which can reverse ten thousand times every day by adopting variable frequency devices or magnetic switches. The disadvantages of the drum type electric-reversing pumping unit are: starting the motor frequently results in high starting current and is less energy efficient. The transducer causes many negative effects during operation, such as network pollution of alternating current power, a harmonic code interference process, a short lifetime because of electrical element heating, etc. In addition, a control system such as a transducer is liable to be affected by working conditions and environmental factors; therefore the flexibility and reliability of the transducer are relatively low.